Initial Results from the LIGO Newtonian Calibrator

TL;DR

The paper presents the Newtonian Calibrator, an innovative gravitational force-based calibration method for LIGO's strain measurements, offering a precise cross-check of existing calibration with less than 1% uncertainty.

Contribution

It introduces a novel calibration scheme using a rotor with quadrupole and hexapole mass distributions to apply predictable gravitational forces on LIGO test masses.

Findings

Force prediction uncertainty <1%

System effectively cross-checks existing calibration

Demonstrates feasibility of gravitational force calibration

Abstract

The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory's test masses. The force produced by this rotor can be predicted to $<1\%$ relative uncertainty and is well-resolved in the readout of the observatory. This system currently acts as a cross-check of the existing absolute calibration system.